prevx, for example, lets you search by filename. plenty of sites have nice
writeups of "what is file foo.exe and what does it do?" for legitimate
files. prevx mostly handles malicious files, and their writeups are vague
or misleading at best in that database.

as for fine grained details sandbox reports are very useful.
threatexpert.com is one of the more comprehensive and searchable. if you
have a file hash (md5) that's the best way to get such details.

virustotal.com is also a useful place to get pointers.

i do not trust or respect most AV writeups, they're very inadequate or
just plain wrong.